Self-pumping heat-pipe fuser roll

ABSTRACT

An energy transfer device includes a heat pipe and at least one spiral feature on an interior surface along a portion of the heat pipe, wherein a pitch of the spiral feature may be such that a liquid is pumped in the heat pipe, and a thermal mass of the heat pipe is reduced by about 50%. The interiro spiral feature may be one of a spiral groove and a spiral fin. A method of manufacturing an energy transfer device may include providing a heat pipe, and providing at least one spiral feature via rotating extrusion on an interior surface along at least a portion of the heat pipe, wherein a pitch of the at least one spiral feature is such that a liquid is pumped in the heat pipe, and a thermal mass of the heat pipe is reduced by about 50%.

BACKGROUND

Maintaining temperature uniformity of a fuser roll has long been aproblem when varying media sizes in printing systems. In order to solvethese uniformity issues, using a heat pipe as a fuser roll has beenpreviously disclosed. Problems generally arise though in the complexityof the design of such heat pipe fuser rolls because the heat pipegenerally acts as a closed system, and applying heat internally becomesdifficult. Previous disclosures recommend applying heat at one end ofthe fuser roll, which simplifies the geometry of the subsystems. Forinstance, the following references describe heat pipes with specificallyconfigured internal structures: U.S. application Ser. No. ______(Attorney Docket No. 122311; Xerox ID # 20040275-US-NP); U.S. Pat. No.4,773,476; “Helical Guide-Type Rotating Heat Pipe”, Shimizu, A. andYamazaki, S., 6^(th) International Heat Pipe Conference, 1987; “HeatTransfer and Internal Flow Characteristics of a Coil-Inserted RotatingHeat Pipe”, Lee, J. and Kim, C., International Journal of Heat and MassTransfer, 2001. A capillary wick is sometimes used to solve thisproblem, but the use of a capillary wick may limit the maximum heat fluxsupported by the heat pipe.

SUMMARY

By applying all the heat at one end of the system, the incident heatflux at that end is increased, and because there is a need to minimizethe amount of water in the heat pipe for instant-on applications, thereis a potential for dry-out, or film boiling, of the heat pipeevaporator. Moreover, inductively heated heat pipe fuser may requirelarger amounts of working fluids to operate at various angles of tilt.Larger amounts of working fluid are required to prevent dry-out at theheated end when the heated end is at a higher elevation that the portionof the heat pipe fuser roll delivering heat to the paper.

In light of these problems and shortcomings, various exemplaryembodiments of devices and methods may provide an energy transfer devicethat includes a heat pipe and at least one spiral feature on an interiorsurface along at least a portion of the heat pipe, wherein a pitch ofthe at least one spiral feature is such that a liquid is pumped in theheat pipe during rotation of the heat pipe when liquid is present in theenergy transfer device, and a pumping rate of the liquid is increasedwhile vapor flow impedance is decreased, and thermal mass is decreasedby about 50%. According to various exemplary embodiments, the heat pipeis a heat pipe fuser roll.

Moreover, various exemplary implementations may provide a manufacturingmethod of an energy transfer device that includes providing a heat pipe,and providing at least one spiral feature via rotating extrusion on aninterior surface along at least a portion of the heat pipe, wherein apitch of the at least one spiral feature is such that a liquid is pumpedin the heat pipe during rotation of the heat pipe when liquid is presentin the energy transfer device, and a pumping rate of the liquid isincreased while vapor flow impedance decreases, and thermal mass isdecreased by about 50%. According to various exemplary embodiments, theheat pipe is a heat pipe fuser roll.

Finally, various exemplary implementations provide a xerographic systemthat includes a heat pipe including at least one spiral feature on aninterior surface along at least a portion of the heat pipe, and acontroller that controls an operation of the heat pipe in thexerographic system, wherein a pitch of the at least one spiral featureis such that a liquid is pumped in the heat pipe during operation of theheat pipe by the controller, and a pumping rate of the liquid isincreased while vapor flow impedance decreases, and thermal mass isdecreased by about 50%. According to various exemplary embodiments, theheat pipe is a heat pipe fuser roll.

BRIEF DESCRIPTION OF THE DRAWINGS

Various exemplary implementations of systems are described in detailwith reference to the following figures, wherein:

FIG. 1 is an illustration of an exemplary internal structure of a heatpipe fuser roll;

FIG. 2 is an illustration of the flow of liquid water through the finsof the exemplary heat pipe fuser roll;

FIG. 3 is a: curve illustrating the flow of the volume of liquid waterwith respect to the number of revolutions of the exemplary heat pipefuser roll; and

FIG. 4 is a flow chart illustrating an exemplary method of manufacturinga heat pipe fuser roll.

DETAILED DESCRIPTION OF EMBODIMENTS

These and other features and advantages are described in, or areapparent from, the following detailed description of various exemplaryembodiments.

FIG. 1 is an illustration of an exemplary internal structure of a heatpipe fuser roll. The heat pipe fuser roll 100 may be produced by arotating die extrusion method, or may be produced with separately woundspirals 110. For example, using separately wound spring-like spirals 110may allow pre-stressing the springs in compression before joining to thecylinder, thus increasing the load carrying capacity and stiffening thestructure of the heat pipe fuser roll 100. For example, in order toaccount for 1000 watts of input, approximately 0.5 cc/sec of liquid tobe transported to the heated end would be required. FIG. 1 illustratesthree spiral fins 110 each with a pitch of about 3 times the diameter ofthe heat pipe fuser roll, which produces troughs for a roughlyhorizontal fuser which are approximately one diameter wide. If the fins110 are 3 mm high and the heat pipe fuser roll 100 is 35 mm in diameter,then the trough volume is about 1.39 cc. In one revolution three troughsmay be passing any axial point. If the structure is 100% efficient,about 4.17 cc/rev of liquid would be pumped, and the rotation speedwould have to be about 0.12 rev/sec, or 7.2 rpm.

FIG. 2 is an illustration of the flow of liquid water through the finsof the exemplary heat pipe fuser roll 200. According to variousexemplary embodiments, a full 3 d, time transient model has a heat pipefuser roll with an inner diameter of about 31.5 mm, fitted with a singlefin 3 mm high with a pitch of 100 mm. An angular speed of 140 rpm, whichis typical of the various fusers, is applied. In FIG. 2, at initial timet=0, quiescent liquid water is assumed within the trough defined by thefin height, which amounts to an initial volume of about 3.22 cc, orabout 4.3% of the total interior volume of the fuser roll 200. As theheat pipe fuser roll rotates, the fin may push the liquid water towardsthe evaporator end as shown in the successive (quarter-revolution)frames 210, 220, 230, 240 and 250 in FIG. 2, which are the equivalent ofsnapshots of the flow of water through the fuser roll. The flow of thevolume of water through the fuser roll 200 is quantified by monitoringthe liquid water volume within the heat pipe fuser roll, as shown inFIG. 3. It should be noted that most of the liquid is forced towards theend of each turn when the trough created by the fins approaches theevaporator end of the pipe. At the end of the first turn, the liquidwater volume may be 1.72 cc, which means that about 3.22−1.72=1.5 cc ofliquid water has been pumped out. According to various exemplaryembodiments, since, at 140 rpm, each turn occurs in about 0.43 s, thepumping rate is of approximately 1.5/0.43=3.5 cc/s, which is generallyvery adequate for a 1000 W input and may require about 0.5 cc/sec.Accordingly, the exemplary fuser roll 200 should easily deliver therequired pumping rate for a desired performance. Since an ordinary heatpipe fuser roll requires approximately 10% volume to be water, theeffects of the above-discussed self-pumping may result in an estimated50% overall decrease in thermal mass of the fuser.

It should be noted that the fuser roll according to various exemplaryimplementations is not always 100% efficient, and the entire liquidvolume is generally not pumped in a single turn because part of theliquid generally overflows to the other side of the fin, as indicated inframes see frames 230 to 250 of FIG. 2. This overflow issue may beremedied by having more fins and/or increasing the fin height. It shouldalso be noted that the device efficiency may decrease as the operatingangular speed increases because, at higher angular speeds, the liquidmay begin to behave as a rigid body attaching itself to the inner wallsof the heat pipe fuser roll.

FIG. 4 is a flowchart illustrating an exemplary manufacturing method ofa heat pipe fuser roll. In FIG. 4, the method starts in step S100, andcontinues to step S110. During step S110, a heat pipe fuser roll may beprovided. The control continues to step S120, during which interior ribsmay be provided to various portions of the heat pipe fuser roll. Theinterior ribs may be either interior spiral grooves or interior spiralfins. The interior ribs may have a pitch of up to three times thediameter of the heat pipe fuser roll, and be configured so as to providemaximum liquid pumping and minimum vapor flow impedance and minimumthermal mass. Next, control continues to step S130, where the heat pipefuser roll is evacuated. Next, control continues to step S140, where theheat pipe fuser roll is filled with water and sealed on both ends. Next,control continues to step S150, where the method ends.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different systems or applications. Also,various presently unforeseen or unanticipated alternatives,modifications, variations or improvements therein may be subsequentlymade by those skilled in the art which are also intended to beencompassed by the following claims.

1. An energy transfer device, comprising: a heat pipe; and at least onespiral feature on an interior surface along at least a portion of theheat pipe, wherein a pitch of the at least one spiral feature is suchthat a liquid is pumped in the heat pipe during rotation of the heatpipe when liquid is present in the energy transfer device, and a thermalmass of the heat pipe is reduced by about 50%.
 2. The energy transferdevice of claim 1, wherein the energy transfer device comprises at leastone of a fuser roll, a photoreceptor, and a paper transport device. 3.The energy transfer device of claim 2, wherein the interior spiralfeature comprises a spiral groove.
 4. The energy transfer device ofclaim 2, further comprising an inductive heater to heat the heat pipe.5. The energy transfer device of claim 4, wherein the inductive heatercomprises induction coils located at least at one of one end of the heatpipe, along a length of the heat pipe, both ends of the heat pipe andinside the heat pipe.
 6. The energy transfer device of claim 1, whereinthe spiral fins are about 3 mm high.
 7. The energy transfer device ofclaim 1, wherein the heat pipe is at least one of about 31.5 mm andabout 35 mm in diameter.
 8. The energy transfer device of claim 3,wherein the spiral fins have a pitch of at least one of about 3 times adiameter of the heat pipe and about 100 mm.
 9. A method of using theenergy transfer device of claim 1, comprising: providing the heat pipeincluding the at least one spiral feature; and rotating the heat pipe topump a liquid at a rate of about 0.5 cc/sec.
 10. A method of using theenergy transfer device of claim 1, comprising: providing the heat pipeincluding the at least one spiral feature; and providing a volume ofliquid of at least one of about 1.39 cc and about 3.22 cc into theenergy transfer device.
 11. A method of using the energy transfer deviceof claim 1, comprising: providing the heat pipe including the at leastone spiral feature; and rotating the heat pipe to pump a liquid at arate of about 4.17 cc per revolution.
 12. A method of using the energytransfer device of claim 1, comprising: providing the heat pipeincluding the at least one spiral feature; and rotating the heat pipe ata speed of at least one of about 7.2 rpm and about 140 rpm.
 13. A methodof using the energy transfer device of claim 1, comprising: providingthe heat pipe including the at least one spiral feature; and supplyingabout 1000 W to 1500 W of power to the heat pipe.
 14. A method ofmanufacturing an energy transfer device, comprising: providing a heatpipe; and providing at least one spiral feature via rotating extrusionon an interior surface along at least a portion of the heat pipe,wherein a pitch of the at least one spiral feature is such that a liquidis pumped in the heat pipe during rotation of the heat pipe when liquidis present into the energy transfer device, and a thermal mass of theheat pipe is reduced by about 50%.
 15. The method of claim 14, whereinthe at least one spiral feature comprises a spiral groove.
 16. Axerographic device comprising the energy transfer device of claim
 1. 17.A xerographic system comprising: a heat pipe fuser roll including atleast one spiral feature on an interior surface along at least a portionof the heat pipe; and a controller that controls an operation of theheat pipe fuser roll in the xerographic system, wherein a pitch of theat least one spiral feature is such that a liquid is pumped in the heatpipe during operation of the heat pipe by the controller.
 18. The energytransfer device of claim 1, further comprising more than one evaporatorsection, and wherein the heat pipe comprises two sets of spiralfeatures, each set of spiral features pumping liquid outward from thecenter of the heat pipe to ends of the heat pipe, and heating providedat each one of the ends of the heat pipe.
 19. The energy transfer deviceof claim 2, wherein the interior spiral feature comprises a spiral fin.20. The method of claim 14, wherein the at least one spiral featurecomprises a spiral fin.